No problems found on any of the 15inch. The 13inch always seems to have issues.
The 15inch is so awesome that it will kill mac pro / mba usage if you have one.
Yes definitely, when I did 4K tests , the iris pro munched between 1-2GB of main memory. That leaves you with 6GB to play with, I don't personally think thats enough.
  Tried to get one in store, but they only stock the 8GB so going to have to wait a week for it to be delivered 
Yes definitely, when I did 4K tests , the iris pro munched between 1-2GB of main memory. That leaves you with 6GB to play with, I don't personally think thats enough.

I'd really suggest going with 16GB, I've been watching my usage over the day i've had the machine and seen it creep up to where 8GB would have to start compressing.
The machine is straggling impressive in every sense.
I did the test of loading my backpack with it instead of my MBA and was pleasantly surprised it barely made a difference.
Battery life is something you will have to keep an eye on as you'll get addicted to the retina screen and will whack up the brightness to maximum but just reducing it to 65% on wifi only , bumped me up over 9 hours usage.

13inch version?I'd really suggest going with 16GB, I've been watching my usage over the day i've had the machine and seen it creep up to where 8GB would have to start compressing.
The machine is straggling impressive in every sense.
I did the test of loading my backpack with it instead of my MBA and was pleasantly surprised it barely made a difference.
Battery life is something you will have to keep an eye on as you'll get addicted to the retina screen and will whack up the brightness to maximum but just reducing it to 65% on wifi only , bumped me up over 9 hours usage.
Here's my prices, EDU + Quidco
15" base - £1,443.60 = £1,393.07
15" base 16gb - £1,579.20 = £1,523.92
15" top - £1,869.60 = £1,804.16